That's a tall order. There are a number of dominant and recessive genes at play here, and with two different breeds, you're looking at a wide array of potential mixing.

Some offspring may have the upright build of a runner, while others stay more horizontal like the Rouen. Then there's the matter of coloring. You make no mention of the subtype of Indian Runner but that's going to play a role too. You may also get some offspring that look exactly like mom or exactly like dad.